1. Field of the Invention
The present invention relates to a mold for the continuous casting of metal. The mold has a pouring portion with cooled long side walls and short side walls, wherein the pouring portion becomes narrower in the shape of a funnel in the casting direction until it reaches the size of the cast strand.
2. Description of the Related Art
The dimensions of the pouring portion are essentially determined by the cross-section of the strand to be cast, the dimensions of the pouring pipe and the depth of immersion of the pouring pipe in the molten metal.
Because of the funnel-shaped configuration of the long side walls, the mold not only narrows in the casting direction, but also a change of the shape of the strand cross-section takes place. Consequently, in contrast to a conventional continuous casting mold with planar walls, additional deformations are imparted on the strand shell when it travels through a funnel-type mold. In order to avoid the generation of surface defects of the cast product, these additional deformations may not exceed a certain boundary value, so that the strand shell is not overloaded and a uniform heat discharge over the cross-section of the strand remains ensured.
EP 0 268 910 B1 proposes to guide the strand shell which is still thin underneath the meniscus without deformation by providing long side walls which in the pouring portion extend essentially parallel to each other in a first section and are reduced to the thickness of the casting size in a subsequent section, wherein the first section extends to below the meniscus level to be adjusted during the casting operation into the area of the first strand shell formation. The entire change of shape to be imparted on the strand by the mold, which is required for reducing the strand to the thickness of the casting size, extends along the subsequent section which is formed by inclined or curved surfaces or combinations thereof.
EP 0 552 501 A2 discloses a mold for the continuous casting of steel strip in which the long side walls form a funnel-shaped pouring portion which is reduced toward the short side walls and in the casting direction to the size of the cast strip. The curvature of the funnel-shaped pouring portion is determined by lateral circular arcs and middle circular arcs connected to the lateral circular arcs at the tangential points. For reducing the friction and wear and for reducing the tensile stress and bending stress of the strand shell, the radii of the lateral circular arcs are uniform in a section which extends at least 100 mm down from the upper edge of the mold.
DE 39 07 351 A1 discloses a proposal for constructing the pouring funnel of a mold in such a way that the deformation of the metal cast strand is distributed over a travel length which is as long as possible and to avoid constrictions and the formation of cracks in the strand shell of the metal cast strand. This is achieved by forming the contour of the inner wall of the pouring funnel in the strand travel direction by three circular arcs which contact each other tangentially, wherein the radii of the circular arcs gradually increase in the strand travel direction and lead into the contour of the inner wall of the mold. A distribution of the change of the shape of the strand shell which is as uniform as possible in a pouring portion shaped in this manner is achieved thereby that the radii of the circular arcs increase in the strand travel direction with equal or unequal factors.